Impact clutch mechanism

ABSTRACT

The pneumatically powered impact clutch mechanism includes a one-piece anvil shaft journalled only at its respective opposite ends; this anvil shaft supports all of the other components of the impact clutch assembly, including a single hammer dog arranged for impacting engagement with an anvil formation integral with the anvil shaft. Thrust bearing means engaged with the anvil shaft and the housing transmit to the latter such axial forces which are applied to the anvil shaft; the thrust bearing means are independent of the other parts of the impact clutch assembly thereby to prevent stalling of the motor as a consequence of such axial forces being transferred to the latter. The output shaft of the pneumatic motor, which has an integral rotor section, is supported by roller bearings and is thereby permitted to float axially; the rotor defines annular faces in close confronting relationship with respect to the end walls of the stator housing. This floating bearing construction facilitates motor manufacture as it permits greater tolerances for the dimensions of the rotor section and the spacing between the stator end walls.

United States Patent [191 Legler Nov. 19, 1974 IMPACT CLUTCH MECHANISM l [75] Inventor: John G. Legler, North Aurora, 111.

[73] Assignee: Skil Corporation, Chicago, Ill.

[22] Filed: Dec. 26, 1973 [21] Appl. No.: 427,734

Primary Examiner-James A. Leppink Attorney, Agent, or Firm-McDougall, Hersh & Scott [57] ABSTRACT The pneumatically powered impact clutch mechanism includes a one-piece anvil shaft journalled only at its respective opposite ends; this anvil shaft supports all of the other components of the impact clutch assembly, including a single hammer dog arranged for impacting engagement with an anvil formation integral with the anvil shaft. Thrust bearing means engaged with the anvil shaft and the housing transmit to the latter such axial forces which are applied to the anvil shaft; the thrust bearing means are independent of theother parts of the impact clutch assembly thereby to prevent stalling of the motor as a consequence of such axial forces being transferred to the lattenThe output shaft of the pneumatic motor, which has an integral rotor section, is supported by roller bearings and is thereby permitted to float axially; the rotor defines annular faces in close confronting relationship with respect to the end walls of the stator housing. This floating bearing construction facilitates motor manufacture as it permits greater tolerances for the dimensions of the rotor section and the spacing between the stator end walls.

11 Claims, 4 Drawing Figures IMPACT CLUTCH MECHANISM BACKGROUND OF THE INVENTION 1. Field Of The Invention The invention relates to hand held power tools referred to in the art as impact wrenches or nut runners. These tools, which are usually pneumatically powered, include impact clutch mechanisms of various designs for imparting continuous rotation to a fastener, such as a nut, until such fastener is partially tightened thereby tending to resist further rotation, whereupon the impact clutch Comes into operation for delivering successive rotary impact blows to the nut for securely fastening the same. More particularly, the present invention relates to improvements in such an impact clutch mechanism and the means powering the latter.

2. The Prior Art Impact wrenches of the type under consideration are well known in the prior art. Representative U.S. Pats. assigned to the assignee of the present application and showing these prior art structures are: Kaman et al., No. 3,228,486; Kaman, No. 3,270,593; and Kaman, No. 3,380,539.

These prior art structures have been generally satisfactory; however, these prior devices all have a common disadvantage in that they permit axial forces, to which the anvil shaft is subjected, to be transferred to the motor thereby tending to slow down or even stall the latter. In the use of these hand held tools, it is normal for the operator to urge the tool against the nut or bolt, as the case may be, to maintain the driving engagement between the tool and the fastener being run. These operator applied forces result in the anvil shaft being subjected to an axial force; that is to say, the anvil is in effect being forced within the housing.

In these prior art structures, the anvil is engaged with one or more of the parts of the impact clutch assembly and/or components of the drive train between the motor and the impact clutch, such that components of the aforementioned axial forces are transferred to the motor tending to slow the same. Accordingly, these prior devices permit a power loss as a consequence of the operator urging the tool against the work.

These prior art devices have further disadvantages in that they include a considerable number of parts and are rather complicated in design thereby making inexpensive manufacture somewhat difficult. Moreover, these prior art devices do not lend themselves to simplified and low-cost manufacturing techniques because their substantial number of parts ,renders the necessary precision alignment a difficult task.

SUMMARY AND OBJECTSOF THE INVENTION The present invention provides an impact clutch mechanism of unique and simplified construction whereby thrust forces are transferred directly from the anvil to the motor housing and independently of the other components of the impact clutch thereby to prevent stalling of the motor as a consequence of said axial forces being transferred to the latter.

A primary object of the present invention is the provision of a new and improved impact clutch mechanism whereby axial thrust forces to which the anvil shaft is subjected are transferred directly to the housing and independently of the other components of the impact clutch mechanism.

Another object of the present invention is the provision of an impact clutch having a unitary anvil shaft which is joumalled adjacent its respective opposite ends.

Still another object of the present invention is the provision of an impact clutch mechanism having a unitary anvil shaft which serves to support all of the other components of the impact clutch.

Yet another object of the present invention is the provision of an impact wrench including an impact clutch mechanism of the type described, and wherein the rotor of the pneumatic motor is solely mounted by roller bearings and thereby permitted to float axially so as to facilitate manufacture of the motor.

These and other objects and advantages of the invention will become apparent from the following specification disclosing a preferred embodiment as shown in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of an impact wrench embodying the present invention;

FIG. 2 is a vertical central section through the impact wrench;

FIG. 3 is an exploded isometric view of the impact clutch mechanism; and

FIG. 4 is an enlarged, fragmentary section showing the thrust bearing for the anvil shaft.

DESCRIPTION OF A PREFERRED EMBODIMENT An impact wrench embodying the present invention includes a housing, generally designated 10, having a motor housing portion 11 and an impact clutch housing portion 12. The present invention has particular, although not exclusive, application in an impact wrench of the type adapted for use in the automotive field; such an impact wrench is small and compact for fitting within the many confined areas found on modem-day automobiles.

An impact clutch mechanism, generally designated 14, is mounted within the housing portion 12. This impact mechanism includes a one-piece anvil shaft, generally designated 15, having one end configured in the form of a square-drive 16 for driving engagement with a socket (not shown), the latter being adapted to engage a nut or bolt head, for example. At this time it should be mentioned that the driving or output end of the anvil shaft may have other configurations. For example, this end of the anvil shaft could be provided with a socket for driving engagement with the member to be rotated; in this respect, reference is made to the aforementioned Kaman US. Pat. Nos. 3,270,593 and 3,380,539.

The housing 12 mounts a ring 17, which ring in turn mounts an annular bearing member 18; this bearing member rotatably engages a cylindrical portion 19 of the anvil shaft thereby joumalling oneend of the latter. The other end of the anvil shaft is defined by a reducedin-diameter cylindrical formation 20 received within the inner race 21 of a ball bearing assembly, generally designated 23. This ball bearing assembly includes a plurality of ball bearings 25 and an outer race 26. The ball bearing assembly 23 is received within a cavity 28 formed in a plate 29, the latter forming part of the housing portion 12. Thus, it is seen that the anvil shaft is journalled for rotation only at areas adjacent its respective opposite ends.

Referring particularly to FIG. 3, the anvil shaft includes a cylindrical portion 31 separated from the cylindrical portion by another cylindrical portion 32, the latter having a diameter less than the diameters of the portions 20 and 31. The juncture of cylindrical portions 31, 32 defines an annular shoulder 34 arranged for abutting engagement with an annular face 21a (FIG. 4) formed on the bearing race 21. Accordingly, it is seen that axial forces applied to the anvil shaft are transmitted to the tool housing via the ball bearing assembly 23. The ball bearing assembly 23 serves both to journal one end of the anvil shaft and to transfer thrust forces from the latter directly to the tool housing.

The impact clutch assembly itself, which is of the general type shown in the expired US. Pat. to Amtsberg, No. 2,768,546, includes. a cam sleeve 36 journalled on the anvil shaft 15, in particular on the cylindrical portion 31 and another cylindrical portion 37 of equal diameter with the portion 31 and separated from the latter by a reduced-in-diameter cylindrical portion 38. The cam sleeve includes a pair of camming ears 40, 41 defining a space or notch 42 therebetween.

The impact clutch assembly further includes a cage, generally designated 43, having a first ring portion 44 journalled on a cylindrical portion 36a of the cam sleeve. The cage includes another ring portion 45 joined with the ring portion 44 by an arcuate wall portion 46. The ring portion 45 receives a bearing ring 48 (FIG. 2) journalled on the cylindrical portion 19 of the anvil shaft 15. Accordingly, it will be appreciated that the anvilshaft supports the cam sleeve 36 and the bearing ring 48; these two parts in turn support or journal the cage 43.

At this time it should be mentioned, that axial movement of the cam sleeve 36 relative to the anvil shaft 15 is restrained by engagement of one end of the cam sleeve with anannular shoulder 50 formed on the anvil shaft at the juncture of portion 37 with an anvil formation 52. The other end of the cam sleeve 36 abutts a spacing washer 53 (FIG. 4).

The impact clutch assembly 14 includes a hammer dog 55 pivotally mounted on a pin 56, opposite ends of the latter being received within bores 47, 48 formed in respective ring portions 44, 45 of the cage 43. The hammer dog includes an upstanding camming lug 60 arranged to be received within the recess 42 of the cam sleeve 36. The hammer dog 55 includes a pair of jaws 61, 62 arranged for impacting engagement with the jaws 63, 64 formed on the anvil portion 52 of the anvil shaft.

It will be understood that the cam sleeve 36 serves to rotate the hammer dog and cage and to rock the hammer dog 55 about the axis defined by the pin 56 for bringing one of the hammer jaws 61, 62 into impacting engagement with one of the anvil jaws 63, 64 when the impact wrench is being operated in a forward direction and for bringing the other of the hammer jaws into engagement with the other of the anvil jaws when the tool is being operated in the reverse direction. For an understanding of the operation of the impact clutch assembly 14, reference should be had to the aforementioned Amtsberg patent as well-as to the Kaman US. Pat. No. 3,380,539. For purposes of the present invention, it is sufficient to say that rotation imparted to' the cam sleeve 36 will cause corresponding rotation of the anvil shaft 15 until the latter resists rotation as a consequence of the driven fastener becoming partly tightened. This resistance to rotation causes the camming mechanism to operate whereupon repeated impacting or hammering blows are transferred to the anvil shaft from the hammer dog 55.

A bevel gear 66 is mounted on the cam sleeve 36. This bevel gear includes a spline formation 67 arranged for engagement within a spline formation 68 formed on the cam sleeve. Accordingly, rotation of the bevel gear 66 is imparted to the cam sleeve 36.

The teeth on the gear 66 are in meshing engagement with the teeth on another bevel gear 70, the latter being mounted on one end of the output shaft 71 forming part of a pneumatic motor, generally designated 72. The gear 70 is mounted on this output shaft in driven relationship therewith, as by means of a spline formation 73. The angular relationship between the axes of the bevel gears 66, 70 is preferably as disclosed and claimed in the above mentioned Kaman US. Pat. No. 3,270,593;

The bevel gear 70 is rotatably mounted by a ball bearing assembly, generally designated 75. This ball bearing assembly is mounted within a ring 76, the latter being suitably mounted within the housing portion 11 of the impact wrench.

The output shaft 71 of the pneumatic motor includes a first cylindrical bearing formation 71a and a second cylindrical bearing formation 71b separated by an en larged, cylindrical formation defining a rotor 77. This rotor includes a plurality of equally spaced, axially and radially extended slots for receiving a corresponding number of vanes; one of such slots 78 is illustrated with the associated vane 79 being received therein. Preferably, a spring 80 is provided for urging the vane 79 outwardly to facilitate starting of the pneumatic motor (of course, such springs are provided for the other vanes in the rotor). I

The motor includes a stator defined by a cylindrical member 80 with a bore 81 eccentrically formed therein. The stator further includes end plates 82, 83 secured to the cylindrical member 80. The plates 82, 83 include respective end walls 84, 85; these walls are in close confronting relationship with respective annular faces 86, 87 defined by the ends of the rotor 77.

The end plate 82 is centrally bored for receiving a roller bearing assembly 88, the latter being engaged with the cylindrical formation 71a of the output shaft. Similarly, the end plate 83 is centrally bored for receiving another roller bearing assembly 89, the latter receiving the cylindrical formation 71b of the output shaft.

Thus, it is seen that the output shaft 71 of the motor is solely journalled by means of the roller bearing assemblies 88, 89 which permit axial movement of the shaft. Consequently, limited axial movement or floating of the rotor 77 is permitted. This floating construction of the rotating member of the pneumatic motor facilitates construction thereof as it reduces somewhat the tolerance considerations for the axial dimension of the rotor 77 and the spacing between the end walls 84, 85. It will be appreciated that the spacing between the end faces of the rotor section 77 and the adjoining stator walls must be maintained to a minimum to prevent blow-by which of course reduces efficiency.

Also, this roller bearing support for the output shaft ensures that the latter will always float axially thereby to prevent undue wear between the end faces 86, 87 of the rotor and the adjoining end walls 84, 85 of the stator. In prior art constructions utilizing one or more ball bearing assemblies for supporting the rotor shaft, quite often a part of such bearing assemblies would freeze and prevent axial movement of the shaft in which event scraping or rubbing of adjoining faces of the rotor and stator would result.

Other than the mounting of the output shaft and rotor, as just explained, the pneumatic motor 72 is conventional and operates in a manner well known to those skilled in the art. The speed and direction of the motor are controlled by a regulator assembly, generally designated 90. This assembly, which is of a type well known to those skilled in the art, includes a regulator knob 91 and an actuator stem 92 arranged to be engaged by the operating trigger or lever 93. A forward-reverse control (not shown) is provided to permit the operator to control the direction of rotation of the motor. The regulator assembly 90 is received within a housing block 94, which block has a threaded bore 95 for receiving a fitting (not shown) on one end of an air hose.

Accordingly, it is seen that the present invention provides a new and improved impact clutch mechanism. Axial thrust forces are transferred to the tool housing from the anvil shaft and independently of all other components of the impact clutch assembly as well as the tool motor. This construction prevents power loss and stalling of the tool motor as a consequence of the operator applying forces to the tool in urging the same against the work.

Further, the one-piece anvil shaft is journalled at its respective opposite ends; this journal construction is especially important when using an impact clutch assembly having only a single hammer dog, as the latter does not of course apply a balanced blow to the anvil formations. The impact clutch according to the present invention includes a bare minimum number of parts thereby providing greater durability and reduced friction as well as permitting simplified and low-cost manufacture. The unitary anvil shaft facilitates precision alignment of the various parts of the impact clutch; this feature also contributes to reduced cost and ease in assembly. Finally, the bearing construction for the rotor of the pneumatic motor facilitates and simplifies its manufacture and contributes to increased durability and reliability.

1 claim:

1. In an impact wrench of the type including an impact clutch mechanism and a motor for powering the same, the improvement comprising:

a. an anvil shaft carrying an anvil formation and having one of its ends configured for transmitting rotation to a member adapted to be engaged by the impact wrench;

. an impact clutch assembly for transmitting continuous rotation to the anvil shaft until the latter resists such rotation and thereafter to impart successive impact blows to the anvil shaft;

connecting means for transmitting rotation from said motor to said impact clutch assembly; and

. thrust bearing means engaged with said anvil shaft and the housing of the impact wrench for transmitting to the latter such axial forces which are applied to the anvil shaft, said thrust bearing means being independent of said impact clutch assembly and said connection means thereby to prevent such axial forces from being transferred to said motor.

2. The improvement according to claim 1 further defined by first and second bearing means engaged with said anvil shaft adjacent respective opposite ends of the latter thereby joumalling the anvil shaft for rotation in said housing.

3. The improvement according to claim 2, wherein a portion of said thrust bearing means is formed by a portion of one of said first and second bearing means.

4. The improvement according to claim 2, wherein said anvil shaft is a one-piece member having said anvil formation integrally formed thereon, and wherein said anvil shaft is solely journalled by said first and second bearing means.

5. The improvement according to claim 1, wherein said connection means includes a gear coaxially mounted with respect to said anvil shaft intermediate the ends of the latter.

6. The improvement according to claim 1, wherein said impact clutch assembly comprises:

a. a cage coaxially mounted with respect to the anvil shaft and with the intermediate portion of the latter received within the cage;

b. a cam sleeve coaxially mounted on said anvil shaft and being interposed between the latter and one end of the cage;

c. said connection means including a gear coaxially mounted on said cam sleeve;

d. spline means connecting said gear with said cam sleeve such that rotation of the former is transferred to the latter; and

e. hammer dog means carried by said cage means and including a formation for impacting engagement with said anvil formation.

7. The improvement according to claim 6, wherein said hammer dog means includes a single hammer dog.

8. The improvement according to claim 1, wherein said anvil shaft supports all of the other components of said impact clutch assembly.

9. The improvement according to claim 8, wherein said connection means includes a gear supported by said anvil shaft in coaxial relationship therewith.

10. The improvement according to claim 1 further defined by:

a. said motor being pneumatically operated and including a stator housing and an output shaft, said output shaft being of unitary construction and including an enlarged, coaxial rotor intermediate the ends thereof, said rotor defining annular faces in close confronting relationship with respective walls of the stator housing, said rotor being provided with a plurality of axial slots receiving a corresponding number of vanes; and

b. first and second sets of roller bearing assemblies engaging said output shaft adjacent its ends thereby 1 1. The improvement according to claim 10, wherein said connection means includes a gear mounted on said output shaft by a spline connection. 

1. In an impact wrench of the type including an impact clutch mechanism and a motor for powering the same, the improvement comprising: a. an anvil shaft carrying an anvil formation and having one of its ends configured for transmitting rotation to a member adapted to be engaged by the impact wrench; b. an impact clutch assembly for transmitting continuous rotation to the anvil shaft until the latter resists such rotation and thereafter to impart successive impact blows to the anvil shaft; c. connecting means for transmitting rotation from said motor to said impact clutch assembly; and d. thrust bearing means engaged with said anvil shaft and the housing of the impact wrench for transmitting to the latter such axial forces which are applied to the anvil shaft, said thrust bearing means being independent of said impact clutch assembly and said connection means thereby to prevent such axial forces from being transferred to said motor.
 2. The improvement according to claim 1 further defined by first and second bearing means engaged with said anvil shaft adjacent respective opposite ends of the latter thereby journalling the anvil shaft for rotation in said housing.
 3. The improvement according to claim 2, wherein a portion of said thrust bearing means is formed by a portion of one of said first and second bearing means.
 4. The improvement according to claim 2, wherein said anvil shaft is a one-piece member having said anvil formation integrally formed thereon, and wherein said anvil shaft is solely journalled by said first and second bearing means.
 5. The improvement according to claim 1, wherein said connection means includes a gear coaxially mounted with respect to said anvil shaft intermediate the ends of the latter.
 6. The improvement according to claim 1, wherein said impact clutch assembly comprises: a. a cage coaxially mounted with respect to the anvil shaft and with the intermediate portion of the latter received within the cage; b. a cam sleeve coaxially mounted on said anvil shaft and being interposed between the latter and one end of the cage; c. said connection means including a gear coaxially mounted on said cam sleeve; d. spline means connecting said gear with said cam sleeve such that rotation of the former is transferred to the latter; and e. hammer dog means carried by said cage means and including a formation for impacting engagement with said anvil formation.
 7. The improvement according to claim 6, wherein said hammer dog meanS includes a single hammer dog.
 8. The improvement according to claim 1, wherein said anvil shaft supports all of the other components of said impact clutch assembly.
 9. The improvement according to claim 8, wherein said connection means includes a gear supported by said anvil shaft in coaxial relationship therewith.
 10. The improvement according to claim 1 further defined by: a. said motor being pneumatically operated and including a stator housing and an output shaft, said output shaft being of unitary construction and including an enlarged, coaxial rotor intermediate the ends thereof, said rotor defining annular faces in close confronting relationship with respective walls of the stator housing, said rotor being provided with a plurality of axial slots receiving a corresponding number of vanes; and b. first and second sets of roller bearing assemblies engaging said output shaft adjacent its ends thereby journalling the latter in said stator housing, said needle bearing assemblies permitting said output shaft to float axially thereby to reduce the criticality of the tolerances between said annular faces of the rotor and said walls of the stator housing.
 11. The improvement according to claim 10, wherein said connection means includes a gear mounted on said output shaft by a spline connection. 